1. Field of the Invention
This invention relates to the field of clutches, more particularly to control systems for engaging and disengaging clutches. The invention pertains to the control of a clutch that driveably connects an automotive engine and a manual transmission.
2. Desription of the Prior Art
A manual transmission for use in an automotive vehicle is generally connected to the engine through a friction clutch whose engagement and disengagement is determined by the manual movement of a clutch pedal under the control of the vehicle operator. In manual countershaft transmissions, an input speed reduction gearset continuously connects the output of the clutch to the countershaft so that as the clutch is engaged the countershaft rotates. The various forward speed ratios of the transmission are produced by gear and pinion pairs including output gears journalled on the output shaft and pinions formed integrally with the countershaft. Synchronizer clutches, each one located between two of the output gears, alternately connect the gears to the output shaft when the synchronizer is moved into engagement with clutch teeth formed integrally with the output gears.
When the vehicle operator places the transmission in the neutral position where the synchronizer clutches are not engaged with either of the associated output gears, the friction clutch is engaged and power is transmitted through the input gearset to the countershaft whose rotation causes all of the output gears that are rotatably supported on the output shaft to turn with the countershaft. While the drive system is so disposed, variations in engine speed will cause the countershaft speed to vary. The clearances present between adjacent teeth on the countershaft pinions and the output gear tooth located between the pinion teeth are continuously undergoing change as the countershaft speed varies. In extreme conditions, while the driveline is set for neutral operation with the clutch engaged, the teeth of the mating gears and pinions impact. This condition called neutral rollover rattle is sensed by the vehicle operator as an unwanted noise produced in the idle condition with the transmission operating in the neutral position.